The most common inherited form of amyotrophic lateral sclerosis (ALS), a neurodegenerative disease affecting adult motoneurons, is caused by dominant mutations in the ubiquitously expressed Cu 2؉ ͞Zn 2؉ superoxide dismutase (SOD1). Recent studies suggest that glia may contribute to motoneuron injury in animal models of familial ALS. To determine whether the expression of mutant SOD1 (mSOD1 G93A ) in CNS microglia contributes to motoneuron injury, PU.1 ؊/؊ mice that are unable to develop myeloid and lymphoid cells received bone marrow transplants resulting in donor-derived microglia. Donor-derived microglia from mice overexpressing mSOD1 G93A , an animal model of familial ALS, transplanted into PU.1 ؊/؊ mice could not induce weakness, motoneuron injury, or an ALS-like disease. To determine whether expression of mSOD1 G93A in motoneurons and astroglia, as well as microglia, was required to produce motoneuron disease, PU.1 ؊/؊ mice were bred with mSOD1 G93A mice. In mSOD1 G93A ͞PU.1 ؊/؊ mice, wild-type donorderived microglia slowed motoneuron loss and prolonged disease duration and survival when compared with mice receiving mSOD1 G93A expressing cells or mSOD1 G93A mice. In vitro studies confirmed that wild-type microglia were less neurotoxic than similarly cultured mSOD1 G93A microglia. Compared with wild-type microglia, mSOD1 G93A microglia produced and released more superoxide and nitrite؉nitrate, and induced more neuronal death. These data demonstrate that the expression of mSOD1 G93A results in activated and neurotoxic microglia, and suggests that the lack of mSOD1 G93A expression in microglia may contribute to motoneuron protection. This study confirms the importance of microglia as a double-edged sword, and focuses on the importance of targeting microglia to minimize cytotoxicity and maximize neuroprotection in neurodegenerative diseases.bone marrow transplant ͉ neuroprotection ͉ superoxide dismutase ͉ nitric oxide ͉ motoneurons

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Free fatty acids (FFAs) play important physiological roles in many tissues as an energy source and as signaling molecules in various cellular processes. Elevated levels of circulating FFAs are associated with obesity, dyslipidemia, and diabetes. Here we show that GPR84, a previously orphan G protein-coupled receptor, functions as a receptor for medium-chain FFAs with carbon chain lengths of 9 -14. Medium-chain FFAs elicit calcium mobilization, inhibit 3,5-cyclic AMP production, and stimulate [ 35 S]guanosine 5-O-(3-thiotriphosphate) binding in a GPR84-dependent manner. The activation of GPR84 by medium-chain FFAs couples primarily to a pertussis toxin-sensitive G i/o pathway. In addition, we show that GPR84 is selectively expressed in leukocytes and markedly induced in monocytes/macrophages upon activation by lipopolysaccharide. Furthermore, we demonstrate that medium-chain FFAs amplify lipopolysaccharidestimulated production of the proinflammatory cytokine interleukin-12 p40 through GPR84. Our results indicate a role for GPR84 in directly linking fatty acid metabolism to immunological regulation.G protein-coupled receptors (GPCRs) 3 constitute one of the largest gene families yet identified (1, 2). It has been estimated that more than half of all modern drugs target these receptors (3, 4). GPCRs contain seven transmembrane domains and are activated by a wide variety of ligand types, including light, ions, amino acids, nucleotides, lipids, peptides, and proteins. In addition to about 250 characterized receptors, over 100 human genes encode proteins that belong to this family of receptors but for which ligands and functions remain to be determined (1). These orphan receptors are expected to play important roles in the regulation of a diversity of physiological functions.In the past decade an increasing number of GPCRs have been deorphanized. Many of the identified ligands are metabolic intermediates, including succinate (ligand for GPR91) (5), ␣-ketoglutarate (ligand for GPR99) (5), fatty acids (ligands for GPR40/41/43/120) (6 -10), ketone body (ligand for HM74a) (11), bile acids (ligands for BG37) (12), and kynurenic acid (ligand for GPR35) (13). We have built a library of biochemical intermediates to test their ability to activate orphan GPCRs. In this report, we have identified medium-chain FFAs as ligands for GPR84. Short-chain and long-chain saturated and unsaturated FFAs, previously shown to activate GPR40/41/43/120 (6 -10), are inactive at GPR84. GPR84 is an orphan GPCR originally isolated using an expressed sequence tag data mining strategy (14) and as a gene differentially expressed in granulocytes (15). No close homologs of GPR84 could be identified, although GPR84 is distantly related to monoamine receptors. Expression analysis revealed significant induction of GPR84 in monocytes/macrophages upon lipopolysaccharide (LPS) stimulation, suggesting that medium-chain FFAs may regulate inflammatory responses through activation of GPR84. EXPERIMENTAL PROCEDURESCloning and Cell Culture-Human and mouse GPR84 ...

Neuroinflammation, marked by gliosis and infiltrating T cells, is a prominent pathological feature in diverse models of dominantly inherited neurodegenerative diseases. Recent evidence derived from transgenic mice ubiquitously overexpressing mutant Cu 2؉ / Zn 2؉ superoxide dismutase (mSOD1), a chronic neurodegenerative model of inherited amyotrophic lateral sclerosis (ALS), indicates that glia with either a lack of or reduction in mSOD1 expression enhance motoneuron protection and slow disease progression. However, the contribution of T cells that are present at sites of motoneuron injury in mSOD1 transgenic mice is not known. Here we show that when mSOD1 mice were bred with mice lacking functional T cells or CD4؉ T cells, motoneuron disease was accelerated, accompanied by unexpected attenuated morphological markers of gliosis, increased mRNA levels for proinflammatory cytokines and NOX2, and decreased levels of trophic factors and glial glutamate transporters. Bone marrow transplants reconstituted mice with T cells, prolonged survival, suppressed cytotoxicity, and restored glial activation. These results demonstrate for the first time in a model of chronic neurodegeneration that morphological activation of microglia and astroglia does not predict glial function, and that the presence of CD4؉ T cells provides supportive neuroprotection by modulating the trophic/cytotoxic balance of glia. These glial/T-cell interactions establish a novel target for therapeutic intervention in ALS and possibly other neurodegenerative diseases.amyotrophic lateral sclerosis ͉ astrocytes ͉ bone marrow transplant ͉ microglia ͉ superoxide dismutase

Amyotrophic lateral sclerosis is a relentless and devastating adult-onset neurodegenerative disease with no known cure. In mice with amyotrophic lateral sclerosis, CD4+ T lymphocytes and wild-type microglia potentiate protective inflammatory responses and play a principal role in disease pathoprogression. Using this model, we demonstrate that endogenous T lymphocytes, and more specifically regulatory T lymphocytes, are increased at early slowly progressing stages, augmenting interleukin-4 expression and protective M2 microglia, and are decreased when the disease rapidly accelerates, possibly through the loss of FoxP3 expression in the regulatory T lymphocytes. Without ex vivo activation, the passive transfer of wild-type CD4+ T lymphocytes into amyotrophic lateral sclerosis mice lacking functional T lymphocytes lengthened disease duration and prolonged survival. The passive transfer of endogenous regulatory T lymphocytes from early disease stage mutant Cu2+/Zn2+ superoxide dismutase mice into these amyotrophic lateral sclerosis mice, again without ex vivo activation, were substantially more immunotherapeutic sustaining interleukin-4 levels and M2 microglia, and resulting in lengthened disease duration and prolonged survival; the stable disease phase was extended by 88% using mutant Cu2+/Zn2+ superoxide dismutase regulatory T lymphocytes. A potential mechanism for this enhanced life expectancy may be mediated by the augmented secretion of interleukin-4 from mutant Cu2+/Zn2+ superoxide dismutase regulatory T lymphocytes that directly suppressed the toxic properties of microglia; flow cytometric analyses determined that CD4+/CD25+/FoxP3+ T lymphocytes co-expressed interleukin-4 in the same cell. These observations were extended into the amyotrophic lateral sclerosis patient population where patients with more rapidly progressing disease had decreased numbers of regulatory T lymphocytes; the numbers of regulatory T lymphocytes were inversely correlated with disease progression rates. These data suggest a cellular mechanism whereby endogenous regulatory T lymphocytes are immunocompetent and actively contribute to neuroprotection through their interactions with microglia. Furthermore, these data suggest that immunotherapeutic interventions must begin early in the pathogenic process since immune dysfunction occurs at later stages. Thus, the cumulative mouse and human amyotrophic lateral sclerosis data suggest that increasing the levels of regulatory T lymphocytes in patients with amyotrophic lateral sclerosis at early stages in the disease process may be of therapeutic value, and slow the rate of disease progression and stabilize patients for longer periods of time.